I have bought a Crafter fx550 of ebay, its arrived and its mint, but the pre amp through my Marshall doesn't work.
I have put brand new battery in.
Do pre amps or pickups die?
Yes. But the most common thing to pack up is the jack socket. Use a multi-meter to check there is resistance across the jack you plug into the amp, then try a different jack cable, then check there is output from the piezo/pick-up (you'll need a very low setting on the meter). If all these tests are OK the pre-amp isn't working.
Turn amp right down; plug lead into amp; turn volume up to 1 or 2; touch the tip of the other end of the lead. Does it make a noise through the amp? If yes, the problem is in the guitar; if no, try a new lead.
Hmmm, the leads is fine i use it with other guitars, thats what makes me think its the pre amp or pickup
Most acoustic pre-amps have some kind of buzz or hum when you turn them up so if there's nothing at all I doubt it's the pick up. It's either the pre-amp or the output jack socket.